Fix crash during user_defined_conversions_2

Temporaries created during user conversion operations were being dropped
before the result of the conversion was able to be used. This fixes that
by temporarily storing the result of the conversion inside the
current Function_Push_Pop context.

include/chaiscript/language/chaiscript_common.hpp

@@ -549,6 +549,11 @@ namespace chaiscript
           m_de.save_function_params(t_params);
         }
 
+        void save_params(std::initializer_list<Boxed_Value> t_params)
+        {
+          m_de.save_function_params(std::move(t_params));
+        }
+
 
         private: